It’s a common argument of the know-it-all teen, fresh from an introductory biology course: “Life is so cushy now,” he might say, “People aren’t even evolving anymore.” As the argument goes, most people live a decently long life and have a chance to pass on their genes, since we aren’t so often being gobbled up by lions or succumbing to now-curable diseases. With this comes a dampening on the forces of natural selection, and a stagnation, or even weakening, of the human species.
But the truth, it seems, couldn’t be more different. Over the past 5 to 10 thousand years, says Nature, reporting on a new study, the genetic diversity in the human population has exploded, a bloom that serves as stage one in the process of evolution.
The human genome has been busy over the past 5,000 years. Human populations have grown exponentially, and new genetic mutations arise with each generation. Humans now have a vast abundance of rare genetic variants in the protein-encoding sections of the genome.
Most of the mutations that we found arose in the last 200 generations or so. There hasn’t been much time for random change or deterministic change through natural selection,” said geneticist Joshua Akey of the University of Washington, co-author of the Nov. 28 Nature study. “We have a repository of all this new variation for humanity to use as a substrate. In a way, we’re more evolvable now than at any time in our history.
Most of the new genetic shifts are extremely rare, appearing in only a small slice of the human population. The researchers look at their newly unveiled realization of the breadth of human diversity in terms of what it could mean for trying to understand the genetic basis of a number of diseases, or in what it tells us about humanity’s evolution history. But what it also means is that—come the emergence of a new disease or the turned tide of the zombie apocalypse—BAM, rapid evolution. Bring it, selection pressures. We got this.
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